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Full text of "Remote Control"

Living Room Baja Buggies 



Make] Projects 

hhiiilH ho/ 1 !/ tuMaal/ chare r\icf*f\\tat* 



build, hack, tweak, share, discover,- 



Living Room Baja Buggies 



Written By: John Mouton 



TOOLS: 



Center punch (1) 

Computer (1) 

Double-sided tape (1) 

Drill bits (1) 

To fit the rivet diameter 

Fake desert landscape (1) 

Heat-shrink tubing (1) 

Heat gun or hair dryer (1) 

Needle Nose Pliers (1) 

PICkit 2 Starter Kit (1) 
For programing 

Philips Screwdrivers (1) 
Large and small 

Rivet gun/ rivets (1) 

Sandpaper (1) 

Side cutters, modeling knife, and 
scissors (1) 

Soldering/desoldering tools (1) 

Wire cutter/stripper (1) 



PARTS: 

Wireless camera and tuner/ receiver (1) 
You need a wireless 9V DC. 300mA A/V 
security camera, and a 9V DC. 500mA 
tuner/receiver with 0.9G frequency 
control. Try tigerdirect.com or 
outpost.com. which are web warehouses 
with variable stock. 

• VGA g o ggles (1) 

Any wireless-capable generic or 
namebrand: try amazon.com or 
tigerdirect.com. 

Tamiya Buggy Car Chassis Set (1) 
#701 12 tamiyausa.com 

Tamiya Atomic-Tuned DC Motor (1) 
#15215 

E-Sky EK2-1003 4-channel radio system 

i in 

Which includes transmitter, receiver, 
and 1 servomotor (mini), or similar radio 
system 

• E-Sky EK2-0500 servomotor (1) 



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Living Room Baja Buggies 
hand electric drill (1) 



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For the camera 

Futaba FM75.470 MHz CH.64 crystal (1) 
For multiple buggies, use different 
crystals in the 75MHz-76MHz range to 
avoid cross -talk. 

Thunder Power lithium polymer (Li-Poly) 
1.320mAh/7.4V. 2-cell rechargeable 
battery (1) 
For the motor 

• 9V battery (1) 
For the camera 

• Apache Smart Charger 2020 (1) 
For charging the Li-Poly batteries 

ElectriFly 2-pin male connectors (1) 
#GPMM3106. for all battery, camera, 
and charging connections 

Servo cable with 1 male S connector (1) 
towerhobbies. com #LXPWB5 

• Male S connector (1) 
For servo cable. Tower #LXPWC3 

• Ferrite ring (1) 
For radiocontrol applications, 
deeteeenterprises. com #K1 003 1 TA 

• Battery holder (1) 
digikey.com #1294K-ND 

• #42" Phillips head screw. #4 flat 
washers (2). and 4-40 steel hex nuts (2) 

i tu 

For tie rod hardware 

• NOTE:(1) 
For the R/C transmitter, receiver, 
servos, and crystal, try hobby lobby, com 
and robots tore, com. For the batteries 
and charger, try rctoys.com and 

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Living Room Baja Buggies 



electrifly.com. 



SUMMARY 

Do you like radio-controlled (R/C) cars? Do you like the desert, but hate the heat? Well, sit 
down and kick back as you engage in the excitement of Living Room Baja Buggy Racing. 

This off-road competition combines the fun of homemade R/C cars with the air-conditioned 
convenience of a fake, indoor desert landscape — without the big dollar price. 

There are no rules, no expensive automotive racing equipment, and a total disregard for 
public safety (because these cars are only 6" long and 4" tall). 

You don't even have to look at your car as you negotiate the terrain — an onboard camera 
and a virtual reality headset can be installed for your lackadaisical safety! 

So chase the dog, race against the kids, or just put the electrons to the PC board and hold 
on for a bug's-eye view of the whole racecourse. It's the best thing to hit urban living since 
the Man Cave. 



Step 1 — Build the buggy chassis. 




• Assemble the buggy chassis set as directed in part 3 of the instructions enclosed in the 
Tamiya Buggy Car Chassis Set box. 

• Drill a hole in the back of the motor/gear bracket housing. You'll use it to rivet on the 9V 
battery holder. Use the same drill bit size as the size of your rivet. 

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Living Room Baja Buggies 



Step 2 



r 



j "T— - 





• Modify the tie rod. Bend and trim a 16-gauge wire to about 1" high with arms that fit against 
the tie rod provided in the buggy car chassis kit, as shown. Then solder the 2 together. 
This will give the servo a way to move the tie rod left, right, up, and down with the 
suspension, thus steering the buggy. 

• Solder one 0.1 -microfarad ( f) capacitor and a 24-gauge wire from each lead of the 
atomic-tuned DC motor to the motor case. Next, solder a third 0.1 f capacitor between 
the leads. This will prevent electrical motor noise from interfering with the receiver circuit. 

• Install the wheels as directed in part 6 of the buggy car instructions. However, don't install 
the roll bar — it will just be in the way later when you install the camera servo and the 
motor-control circuit board. 



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Living Room Baja Buggies 



Step 3 — Build the motor-control circuit. 




• Get a printed circuit board. I emailed the schematic and Gerber files provided at 
makezine.com/14/ bajabuggy to Circuit Express (circuitexpress.com). I chose their least 
expensive package, 10 boards for $120, and they built the boards and mailed them to me 
within 24 hours. Other vendors are less expensive for smaller quantities. Or you can buy a 
PCB build kit and make it yourself. 

• Install the circuit components. All components used in the motor-control circuit can be 
purchased from Digi-Key (digikey.com) or any other electronic components supplier. For 
the battery, camera, and charger connections, I used ElectriFly 2-pin male connectors to 
ensure safe, secure connections. I chose the PIC12F683 MCU because it's small, has a 
pulse-width modulation (PWM) module onboard, and is very simple to work with. Here's 
what the completed circuit board should look like after all the components are soldered. 
Use the schematic to guide you. 

• A list of components and part numbers is available at 
http://www.makezine.com/14/bajabuggy . 



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Living Room Baja Buggies 



Step 4 — Install circuit board, battery holder, and servo motors. 






• Before you solder the motor leads, twist them around each other. This will keep electrical 
motor noise from interfering with the receiver. Now solder them to the circuit board at the 
locations marked M1 and M2. 

• Use a small piece of double-sided tape to attach the circuit board to the wooden chassis, 
all the way back so that it touches the motor/gear bracket housing 

• To install the 9V battery holder, first sand off about 5" of its bottom end. This ensures that 
the battery will fit flush inside, and that the holder itself will fit evenly and spaciously 
between the rear wheels. 



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Living Room Baja Buggies 



Step 5 




• Drill a hole in the center of the battery holder the same diameter as the hole you drilled in 
the motor/gear bracket. Then rivet the battery holder to the motor/ gear bracket housing. 

• Extend the battery holder's positive and negative leads by soldering 24-gauge wires to 
them, long enough to comfortably reach J4 on the motorcontrol circuit board. Solder a 2- 
pin male connector to the ends of these wires, which will allow you to disconnect the 9V 
camera battery from the circuit board as needed. 

• Using a small piece of double-sided tape, attach 1 servomotor to the motor-control circuit 
board as close to the motor/gear bracket housing as possible. This servo will be used to 
pan the wireless camera that will be mounted on top of it. 

• The servos come with an assortment of lever arms that can be attached to them, 
depending upon the application. Use the circular lever arm on the camera servo. 



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Living Room Baja Buggies 



Step 6 




• Next, attach the other servo to the chassis just in front of the circuit board. This second 
servo will be used to steer the buggy. 

• For the steering servo, use the straight lever arm. Drill a small hole in the lever arm the 
diameter of a #4 screw. Use the #4 screw, 2 washers, and two #4 nuts to loosely attach 
your modified tie rod to the servo lever arm. Now, as you drive the car over rough terrain, 
the servo will still be able to steer the front wheel even as the front suspension moves up 
and down. 



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Living Room Baja Buggies 



Step 7 — Install the R/C receiver and wireless camera. 





• You can use just about any R/C transmitter/receiver set for this project. If you don't 
already have a set, shop around for a good deal. I found a great deal on a 4-channel radio 
system kit that included the transmitter, receiver, and 1 servo for $60. 

• The reason I chose a 4-channel dual stick transmitter (rather than a 2-channel pistol-type 
transmitter) is because I needed the second left-to-right stick to pan the camera. 

• Using double-sided tape, attach the receiver to the top of the steering servo. To reduce the 
receiver's bulkiness, remove its cover. This allows you to easily install frequency crystals 
and plug components into the receiver. 

• Plug the camera servo into channel 4, and the steering servo into channel 1 . Plug 
connection JP1 of the motor-control circuit board into channel 3 of the receiver; this 
connection will supply power to the receiver and allow you to control the speed of the 
motor via the PWM signal generated from the PIC12F683 MCU. 

• Make the PWM signal cable by crimping the male S connector's pins to the bare-wire end 
of the male servo cable using a pair of pliers. Now, in order to reduce electronic noise 
interference, loop the PWM cable through a ferrite ring before plugging it into channel 3 of 
the receiver. This ring will increase the cable's inductance, thereby filtering out high- 
frequency electronic noise. 

• When using R/C transmitters and receivers for cars, keep them in the R/C car 
frequency range of right around 75MHz. R/C airplanes operate right around the 
72MHz frequency range. 



A 



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Living Room Baja Buggies 



Step 8 




• Before installing the wireless camera to the camera servo, shorten the camera's cable and 
solder another 2-pin male connector so it will plug into the motor-control circuit board at 
J3. To do this, cut the camera's cable down to about 3". Strip 1" of insulation and slide on 
a 2" piece of heat-shrink tubing. Then solder the black and red wires to the 2-pin 
connector, slide the heatshrink tubing over the connection, and shrink it with a heat gun or 
hair dryer. 

• Using your double-sided tape, attach the wireless camera to the camera servo temporarily 
(you'll adjust it later). 



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Living Room Baja Buggies 



Step 9 — Install the motor battery and program the PIC micro-controller. 



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Living Room Baja Buggies 




a 



• For the motor's power source, you 
need something that will supply 
enough voltage and last a while 
between charges. I used a Thunder 
Power lithium polymer (Li-Poly) 
1,320mAh/7.4V2-cell rechargeable 
battery. I don't recommend using 
less than a 480mAh/7.4V battery, 
as it would need to be recharged 
more often. 

• The battery will have a 
charge even if you buy it 
brand-new, so keep the 2 wires 
from touching! 

• Strip the black and red wires 
coming off the battery. Solder the 
wires to another 2-pin male 
connector, and heat-shrink. Attach 
the battery to the 9V battery holder 
with double-sided tape, and 
connect the rechargeable's wires to 
J5 (VBAT) on the circuit board. 

• To program the PIC MCU, I used a 
PICkit 2 Starter Kit (#DV164120) 
that I bought from my company, 
Microchip Technology , for $50. 
This kit has everything you need to 
write, debug, and program your 
source code directly into the MCU 
via header J2 on the circuit board. 

• (If you're a student or educator, 
visit http://microchip.com/academic 
to learn how you can get a discount 
on development tools through 
Microchip's Academic Program.) 



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Living Room Baja Buggies 



Step 10 — Charge it up. 



Goto 

http://makezine.com/14/bajabuggy . 
All you have to do is to import the 

carprogorig.hex program file 
using the PICkit 2 Starter Kit 
interface, and then click the 
Program button. 




• Now that your buggy is assembled, you're almost ready to turn it on. However, you might 
want to charge the battery first. I used an Apache Smart Charger 2020 designed 
specifically for charging 2-cell Li-Poly batteries. 



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Living Room Baja Buggies 

Step 11 — Zero the servos and set the radio controls. 

• You're now ready to fire up your buggy. Once you turn on S1 on the circuit board, the 
servos will power up and find their neutral positions. Hence, you will need to detach the 
camera and reattach it so it faces toward the front of the car. (Good thing you used double- 
sided tape!) You may also need to make a slight adjustment to the steering servo. Simply 
remove the screw holding the lever arm to the servomotor, pull it off, and reattach it, 
pointing straight up. Now, when you turn S1 off and then turn it back on, the servos will be 
aligned to the correct starting points. 

• With the circuit board and hand-held transmitter both turned off, adjust the transmitter 
toggle switches in the lower right-hand corner to set the left control stick (forward and 
back) as the throttle; the left control stick (left and right) for steering; and the right control 
stick (left and right) for panning the camera. The radio system kit's instruction manual will 
help you do this. 

• When finished, turn the transmitter on, then turn the circuit board power on at S1 . Take the 
throttle control stick on the transmitter and pull it all the way back toward you. Then push it 
all the way forward, then back to center. This will establish the maximum duty cycles for 
forward and reverse, and arm the speed control circuit. At this point, the buggy is ready to 
roll. 



Step 12 — Connect the VR goggles. 

• Plug the VR goggles (or a TV monitor) into the receiver that came with the wireless 
camera. Plug the receiver into an AC outlet. Adjust the tuning knob until a picture of what 
the camera sees comes up. I found that the wireless camera range is more than 500' 
straight line-of-sight, with no major obstacles. If you use it outside in a large open area, the 
range is even better. 



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Living Room Baja Buggies 



Step 13 — Resources 

• Download the Baja buggy motor control program for your PIC microcontroller, 
carprogorig.hex, as well as the Gerber files and circuit schematic from 
http://www.makezine.com/14/bajabuggies . You can also download an Excel file listing all 
the Digi-Key part numbers for components that fit this circuit board. And finally, there's a 
list of lower-cost build alternatives provided. 

• Microchip's Online Motor Control Design Center ( http://www.microchip.com/motor ) has a 
wealth of resources for programming your PIC microcontroller to control motors and more. 



This project first appeared in MAKE Volume 14 , page 97. 

This document was last generated on 201 2-1 0-31 1 0:52:35 PM. 



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